This invention relates to the field of electronic ignition systems and, more particularly, to the provision of an essentially noise-immune crankshaft position detector circuit to be used for ignition control.
In the development of distributorless electronic ignition systems, many combinations of crankshaft portions with sensors for sensing the passing of each portion have been utilized. The combination of two sensors and three tabs or projections as shown herein forms a part of the prior art in this field, and the two sets of three pulses per crankshaft revolution are used in a system of which the present invention preferrably forms a part. There are however, problems in obtaining a desired control signal having only two pulses per crankshaft revolution from these two sets of pulses.
Also, since extraneous noise, and even the spark itself, can conceivably produce simultaneous pulses in the two sensor circuits, in addition to the pulses related to the flywheel projections, it is desirable to be able to prevent coincidental pulses from producing unwanted detects in the ignition system. It is also desirable to prevent any cylinder from being fired until the exact crankshaft position is known.